The stock had been sailing along near its all-time high of $360 a share on Wall Street on Thursday lunchtime when it suddenly fell to around $350 in the space of four minutes.

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Medical leave: Steve Jobs speaks to his employees during an Apple event at the company's headquarters in Cupertino, California, in October

The mini-collapse shaved $9.9billion from Apple’s value before the stock began to rebound.

STEVE JOBS - A TIMELINE

February 24, 1955 - Born in San Francisco, California

1976 - After dropping out of college, he founds Apple with Steve Wozniak and Ronald Wayne

1985 - Forced out of Apple and starts the NeXT Corporation

1996 - Returns to his old company when Apple buys NeXT and soon becomes its CEO

2004 - Diagnosed with pancreatic cancer

Late 2008 - Has liver transplant as part of treatment for pancreatic cancer

Early 2009 - Takes six months off to recuperate

January 2011 - Announces he is taking a third leave of absence for medical reasons

It came just a day after experts predicted the California-based company was on course to leapfrog oil monolith Exxon Mobil to become the world’s most valuable firm. And it left traders baffled over what triggered the dramatic blip in the company’s fortunes.

Financial analyst Andy Zaky told CNN: ‘The selling is not normal just for negative news. There was a huge spike where dollars were being skipped in the selling. There’s something else. It wasn’t orderly.'

The smaller-than-expected lines for iPhones being sold by U.S. company Verizon was put forward initially as a possible reason for the sell-off.

But that was swiftly disregarded amid renewed speculation over the health of Mr Jobs, who announced last month that he was going on medical leave.

The importance of the innovative 55-year-old Apple boss’s role is such that his heath has been looked upon as a bellwether to the company’s fortunes.

Nobody appears to know where the hospital rumour started, but he was reportedly seen at Apple’s HQ in Cupertino in recent days looking healthy.

Mr Jobs was also spotted having an Indian meal in nearby Mountain View on Thursday. He is said to be staying closely involved in the company’s affairs, taking business meetings at home and on the phone.

He was treated for a rare form of pancreatic cancer in 2004 and had a liver transplant two years ago. Apple has refused to comment any further about his health.

In healthier times: Mr Jobs introduces the Power Mac G4 in 1999. He was first diagnosed as suffering from pancreatic cancer in 2004

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As Apple shares drop, Steve Jobs is said to be still calling the shots